Zinc-containing optical glass materials

ABSTRACT

Zinc-containing optical glass materials with a refractive index n d  between 1.52 and 1.66, an Abbe number ν d  of between 35 and 54 and a composition (in % by weight based on oxide) of: SiO 2  38–58, ZnO 0.3–42, PbO 0–&lt;30, ZnO+PbO 20–55, Li 2 O 0–&lt;3, Na 2 O 0–14, K 2 O 0–12, Li 2 O+Na 2 O+K 2 O ≧2, F 0–3, MgO 0–6, CaO 0–&lt;5, SrO 0–6, BaO 0–&lt;0.9, B 2 O 3  0–&lt;1, Al 2 O 3  0–&lt;1.5 and ZrO 2  0–&lt;2 and, if appropriate, refining agents in the customary amounts.

This application is a continuation of U.S. Application No. 09/727,998,filed on Dec. 1, 2000 now U.S. Pat. No. 6,806,216.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to zinc-containing optical glass materials whichhave refractive indices n_(d) of from 1.52 to 1.66 and Abbe numbersν_(d) of from 35 to 54.

2. Background Information

During the production of optical glass materials, in addition to anaccurate setting of the required optical properties and achieving a hightransmission, the production costs and raw materials costs play animportant role.

The latter can be achieved in particular by using inexpensive batch rawmaterials and by glass compositions which require relatively low meltingtemperatures and therefore entail lower energy costs.

A large proportion of the known glass materials which have theabovementioned optical properties (refractive indices, Abbe numbers)belong to the group of barium flint glasses. To set the desired opticalproperties and to achieve high transmission, substantially thehigh-quality and expensive raw materials from the group consisting ofthe alkaline earth metal oxides (BaO, SrO, CaO) and PbO are used.

Since the glass components BaO and PbO have become the subject of publicdiscussion in terms of the environmental pollution which they cause, themanufacturers of optical equipment need optical glass materials whichcontain the smallest possible amounts of these components.

Partially or completely substituting one glass component with one ormore other glass components does not generally allow the requiredoptical properties to be reproduced. Instead, new developments orfar-reaching changes in the glass composition are required.

The patent literature includes a number of documents which alreadydescribe glass materials with optical characteristics from the saidrange and with similar compositions. However, these glass materialsexhibit a wide range of drawbacks:

In addition to from 7 to 30% by weight ZnO, the glass materials fromJapanese document JP 85-24060 B2, with refractive indices n_(d) of from1.59 to 1.63 and Abbe numbers ν_(d) from 36 to 50, also contain thecritical components BaO and PbO, in each case in an amount of from 1 to21.5% by weight.

The BaO content of from 0.9 to 15.7% by weight which is providedaccording to SU 1534979 A1 and is absolutely necessary is to be regardedequally critically; these glass materials exhibit a refractive indexn_(d) of from 1.577 to 1.634.

Japanese document JP 89-133956 A relates to optical glass materials withrefractive indices n_(d) of between 1.51 and 1.59 and Abbe numbers ν_(d)of between 39 and 58, which, although only optionally, contain up to44.06% by weight PbO, up to 25.34% by weight B₂O₃, up to 19.06% byweight SrO and up to 11.3% by weight CaO. In addition, these glassmaterials contain relatively large amounts of Al₂O₃ ranging from 4.45 to44.10% by weight, which entails an increase in the melting temperature.Also, from 0.08 to 8.0% by weight F is absolutely imperative.

Moreover, the glass materials may contain in total up to 11.1% by weightAs₂O₃ and Sb₂O₃. When these components are used in such high quantities,increased safety provisions are required during production.

At n_(d) of ≧1.62, the glass materials from document JP 89-308843 A haverelatively high refractive indices, while their Abbe numbers arerelatively low at ν_(d)≦37. In addition to possible high levels of BaO,SrO and CaO, a high PbO content of some 30 to 58% by weight isabsolutely imperative.

With an n_(d) of from 1.62 to 1.85, the optical glass materialsdescribed in document JP 85-221338 A likewise exhibit relatively highrefractive indices, the glass materials containing at least 1 to 50% byweight B₂O₃ and, if only optionally, high levels of BaO (0 to 50% byweight), SrO (0 to 40% by weight), CaO (0 to 30% by weight) and PbO (0to 30% by weight). B₂O₃ reduces the chemical-durability of the glassmaterials.

This also applies to the optical glass materials described in documentSU 97 56 17 which, in addition to a B₂O₃ content of from 2 to 90% byweight, also include CaO (5 to 10% by weight).

The borosilicate glass materials described in document U.S. Pat. No.4,562,161 likewise exhibit the said optical range, but contain at least3% by weight B₂O₃ and at least 4% by weight TiO₂, TiO₂ having an adverseeffect on the transmission, in particular in the UV range.

German document DE 97 33 50 describes optical glass materials whichcover a relatively wide range of refractive indices (n_(d) 1.43 to 1.77)and Abbe numbers (ν_(d) 28 to 67) and therefore have broad compositionalranges. In addition to the strikingly high optional content of up to 50%by weight PbO, the glass materials contain from 0.2 to 30% by weightTiO₂ and from 1.0 to 12% by weight F.

In addition to the principal component SiO₂, the optical glass materialsdescribed in document JP 85-122747 contain a relatively high level offrom 5 to 30% by weight CaO, and the high Abbe numbers ν_(d) which canbe achieved lie in the range from 51 to 57.

The cesium-containing optical glass materials described in document DE22 63 501 C2 likewise cover a range of relatively high Abbe numbersν_(d) of from 50 to 60. The component Cs₂O, which is employed in anamount of between 5 and 82.5% by weight, makes the glass materialconsiderably more expensive.

The Al₂O₃-containing (4–16% by weight) glass materials with a relativelylow alkaline metal content (Na₂O+K₂O 1 to 9.5% by weight) described indocument JP 07 06 18 36 A are not used as optical glass materials, butrather for specific magnetic applications which require the componentsFeO₂ and MnO₂ which are described.

In the glass material which can be doped with Er₂O₃ according to EP 0673 892 A2, which contains from 1.5 to 4% by weight Al₂O₃, B₂O₃ isreplaced by PbO and/or P₂O₅ in order to improve the spectroscopicproperties as optical intensifiers.

The use of ZrO₂, such as for example in the spectacles glass materialsdescribed in U.S. Pat. No. 2,433,833 (2 to 15% by weight ZrO₂) and GB 2233 781 A (5.71 to 23.15% by weight ZrO₂) and in the TiO₂-containingoptical glass materials described in EP 0 287 345 A1 (at least 2.3% byweight ZrO₂), increases the temperature required to melt the glassmaterials.

The optical glass materials described in JP 82 22 139 A contain, interalia, 52 to 75% by weight SiO₂, 5 to 25% by weight ZnO and 3 to 15% byweight Li₂O. However, the essential feature of these glass materials isnot the compositional range, but rather the refractive index which isaltered by ion exchange in an NaNO₃ molten material.

The document JP 87-12633 A describes optical glass materials withgradually adjustable refractive indices; in these materials,substantially cesium undergoes ion exchange against zinc or againstother divalent elements. The glass materials are distinguished inparticular by their cesium content of approximately 2.86–66.25% byweight Cs₂O.

OBJECT OF THE INVENTION

The object of the invention is therefore to provide optical glassmaterials with a refractive index n_(d) of from 1.52 to 1.66 and an Abbenumber ν_(d) of from 35 to 54 which exhibit high transmission, highcrystallization stability and good melting and processing properties andcan be produced at low cost.

SUMMARY OF THE INVENTION

This object is achieved in zinc-containing optical glass materials witha refractive index of 1.52≦n_(d)≦1.66 and an Abbe number of 35≦ν_(d)≦54,characterized by the following composition (in % by weight based onoxide) of: SiO₂ 38–58, ZnO 0.3–42, PbO 0–<30, ZnO+PbO 20–55, Li₂O 0–<3,Na₂O 0–14, K₂O 0–12, Li₂O+Na₂O+K₂O ≧2, F 0–3, MgO 0–6, CaO 0–<5, SrO0–6, BaO 0–<0.9, B₂O₃ 0–<1, Al₂O₃ 0–<1.5 and ZrO₂ 0–<2 and, ifappropiate, refining agents in the customary amounts.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The glass materials contain, as network former, from 38 to 58% by weightSiO₂; if the SiO₂ content rises to above 58% by weight, the meltingtemperature rises disadvantageously while the refractive indices aresignificantly reduced.

In addition to SiO₂, ZnO, in an amount of from 0.3 to 42% by weight,forms the principal component of the glass materials. Together with PbO,the level of which is restricted to from 0 to <30% by weight, ZnO actsas both a network former and a network modifier.

The total ZnO and PbO content is in the range from 20 to 55% by weight.Preferably the total ZnO and PbO content is in the range from >21 to 55%by weight. With high ZnO and PbO contents, high refractive indices n_(d)are established. Varying the ZnO to PbO ratio is used to set the Abbenumbers; low Abbe numbers are achieved with high levels of PbO.

The fact that the glass materials are easy to melt is attributable totheir total Li₂O, Na₂O and K₂O content of at least 2% by weight, theLi₂O content being restricted to 0 to <3% by weight, the Na₂O contentbeing restricted to 0 to 14% by weight, and the K₂O content beingrestricted to 0 to 12% by weight.

It is possible to add small amounts of Al₂O₃ (0 to <1.5% by weight) andB₂O₃ (0 to <1% by weight) which likewise reduce the meltingtemperatures. However, excessively high Al₂O₃ contents cause themeltability to deteriorate. Elevated B₂O₃ contents have an adverseeffect on the chemical durability, in particular with respect to mediacontaining alkaline metals.

High-melting components are substantially eliminated. For example, theZrO₂ content is limited to 0 to <2% by weight.

In subordinate amounts, the glass materials, in particular in order tofine tune their optical properties, may contain from 0 to 6% by weightMgO, from 0 to <5% by weight CaO, from 0 to 6% by weight SrO and/or from0 to <0.9% by weight BaO, the glass materials preferably containing from0 to <0.5% by weight BaO and particularly preferably being substantiallyfree from BaO. The total CaO and SrO content is preferably in the rangefrom 0 to 5% by weight.

Furthermore, from 0 to 3% by weight F is provided. The ranges of theoptical data exhibited by the glass materials are restricted inaccordance with the restrictions on the particular ranges of thecomponents.

For example, glass materials with refractive indices n_(d) of from 1.54to 1.64 and Abbe numbers ν_(d) of from 40 to 52 are obtained within thefollowing compositional range (in % by weight based on oxide): SiO₂39–54, ZnO 12–41, PbO 6–22, ZnO+PbO 31–52, Li₂O 0–<3, Na₂O 0–13, K₂O0–11, Li₂O+Na₂O+K₂O≧2, F 0–3, MgO 0–6, CaO 0–<5, SrO 0–6, BaO 0–<0.9,B₂O₃ 0–<1, Al₂O₃ 0–<1.5 and ZrO₂ 0–<2.

Glass materials with refractive indices n_(d) of between 1.56 and 1.63and Abbe numbers ν_(d) of between 42 and 52 are within the followingcompositional range (in % by weight based on oxide): SiO₂ 40–55,preferably SiO₂ 40–53, ZnO 26–41, preferably ZnO 28–41, PbO 1–16,ZnO+PbO 31–48, Li₂O 0–<3, Na₂O 0–12, K₂O 0–10, Li₂O+Na₂O+K₂O ≧2, F 0–3,MgO 0–6, CaO 0–<5, SrO 0–6, BaO 0–<0.9, B₂O₃ 0–<1, Al₂O₃ 0–<1.5 and ZrO₂0–<2.

Refractive indices n_(d) from 1.60 to 1.63 and Abbe numbers ν_(d) offrom 43 to 47 are obtained with glass materials within the followingcompositional range (in % by weight based on oxide): SiO₂ 40–47, ZnO32–41, PbO 5–14, ZnO+PbO 40–48, Li₂O 0–<3, Na₂O 0–14 preferably 0–13 andparticularly preferably 0–12, K₂O 0–12 preferably 0–11 and particularlypreferably 0–10, Li₂O+Na₂O+K₂O≧2, F 0–3, MgO 0–6, CaO 0–<5, SrO 0–6, BaO0–<0.9, B₂O₃ 0–<1, Al₂O₃ 0–<1.5 and ZrO₂ 0–<2.

Glass materials from the compositional range (% by weight based onoxide): SiO₂ 41–50, ZnO 30–40, PbO 0–1, ZnO+PbO 31–41, Li₂O 0–<3, Na₂O0–11, K₂O 0–10, Li₂O+Na₂O+K₂O≧2, F 0–3, MgO 0–6, CaO 0–<5, SrO 0–6, BaO0–<0.9, B₂O₃ 0–<1, Al₂O₃ 0–<1.5 and ZrO₂ 0–<2, have refractive indicesn_(d) of between 1.57 and 1.59 and Abbe numbers ν_(d) of between 48 and52.

To vary and precisely adapt the optical properties, the glass materialsmay contain up to 2.5% by weight Cs₂O and/or up to 5% by weight Rb₂O,La₂O₃, Y₂O₃ and/or GeO₂.

The optical glass materials claimed preferably have a very high puretransmission of at least 0.98, determined for a wavelength of 400 nm anda specimen thickness of 25 mm.

A further advantage of the glass materials according to the invention istheir neutral colour. Therefore, if preferably up to 8% by weight ofcolouring components are added to the glass compositions described, thecharacteristic spectrum of the colouring components used, such as forexample CuO, Cr₂O₃, CoO, Fe₂O₃, MnO, NiO and/or V₂O₅, are particularlyvalid.

Optical glass materials which have been coloured in this way are used,for example, as optical filters.

To improve the quality of the glass, it is possible for one or moreknown refining agents to be added in the customary amounts to the batch,in order to refine the glass material. As a result, the glass materialhas a particularly good internal quality in terms of its freedom frombubbles and cords.

Preferred refining agents are Sb₂O₃ and/or As₂O₃ the level of whichshould be restricted to at most 1% by weight, preferably 0.5% by weight.

In addition to the desired optical properties, the glass materialsaccording to the invention have the following qualities:

It has been possible to substantially minimize the use of the previouslycustomary but relatively expensive glass components BaO, SrO and CaO. Inparticular, it was possible to further minimize the use of the criticalcomponents BaO and PbO.

This was achieved by introducing the inexpensive, ecologically tolerablecomponent ZnO.

Furthermore, the glass materials exhibit good crystallization stability;furthermore they are not only easy to process, but also can be meltedwith ease.

The glass materials exhibit a sufficiently high chemical durability. Thechemical durability is important in particular for the further machiningof the materials, for example grinding and polishing.

The above-discussed embodiments of the present invention will bedescribed further hereinbelow. When the word “invention” is used in thisspecification, the word “invention” includes “inventions”, that is, theplural of “invention”. By stating “invention”, the Applicants do not inany way admit that the present application does not include more thanone patentably and non-obviously distinct invention, and maintains thatthis application may include more than one patentably and non-obviouslydistinct invention. The Applicants hereby assert that the disclosure ofthis application may include more than one invention, and, in the eventthat there is more than one invention, that these inventions may bepatentable and non-obvious one with respect to the other.

EXAMPLES

24 examples of glass materials according to the invention were meltedfrom standard raw materials.

The glass materials described were produced as follows: the rawmaterials for the oxides, which in some cases were used in the form ofcarbonates and/or nitrates, were mixed and melted at 1300–1350° C. Therefining took place at temperatures of between 1300 and 1400° C. Thiswas followed by a good level of homogenization. Casting of the glassmaterial into the desired shape was carried out at 1220–1270° C.

Table 2 lists the respective composition (in % by weight based onoxide), the refractive index n_(d), the Abbe number ν_(d) and the puretransmission τ_(i) for a wavelength of 400 nm and a specimen thicknessof 25 mm.

In a comparison between a standard barium flint glass of similar opticalproperties, such as for example BaFN₆ (with n_(d)=1.589 and ν_(d)=48.45)in accordance with the SCHOTT catalogue with a pure transmission ofτ_(i,400 nm)=0.93, and Example 15 (with n_(d)=1.59 and ν_(d)=48.4) witha pure transmission of τ_(i,400 nm)=0.99, the improved transmission ofthe glass materials according to the invention becomes clear.

Table 1 shows an example of how to melt the composition for Example 6listed in Table 2.

For Example 6, the devitrification behaviour was also determined. Thisshowed that, as the temperature rose, there was no crystallization evenafter tempering for 60 min in a temperature range from 650 to 1050° C.

TABLE 1 Example of how to melt 100 kg of calculated glass (Example 6,Table 2) Weighed-in Oxide % by weight Raw material quantity [kg] SiO₂50.5 SiO₂ 50.70 ZnO 4.8 ZnO 4.85 PbO 28.2 Pb₃O₄ 28.96 Na₂O 6.7 Na₂CO₃11.46 K₂O 9.6 K₂CO₃ 14.06 As₂O₃ 0.2 As₂O₃ 0.20 Sum 100.0 110.23

TABLE 2 Glass composition (in % by weight based on oxide) andsignificant properties of the glass materials Example 1 2 3 4 5 6 7 8 910 SiO₂ 52.1 54.6 40.0 54.8 40.5 50.5 53.0 41.0 50.9 46.4 ZnO 3.8 22.03.0 34.6 21.0 4.8 10.0 34.9 17.6 27.0 PbO 28.4 1.8 29.0 1.9 29.8 28.223.9 15.5 19.4 10.1 Li₂O — — 2.8 — — — — — — Na₂O 6.6 11.6 13.0 5.2 5.26.7 5.9 5.2 8.2 9.8 K₂O 8.9 9.8 12.0 3.3 3.3 9.6 6.2 3.2 3.7 6.5 B₂O₃ —— — — — — — — — — Al₂O₃ — — — — — — — — — — As₂O₃ 0.2 0.2 0.2 0.2 0.20.2 0.2 0.2 0.2 0.2 ZnO + PbO 32.2 23.8 32.0 36.5 50.8 33.0 33.9 50.4 3737.1 n_(d) 1.57 1.54 1.61 1.57 1.64 1.57 1.57 1.63 1.58 1.58 v_(d) 42.852.8 37.7 51.9 38.1 42.8 44.7 42.3 45.0 47.2 τ_(1400 nm·25 mm) 0.997n.d. n.d. n.d. n.d. 0.998 0.996 n.d. 0.997 0.992 Example 11 12 13 14 1516 17 18 19 SiO₂ 42.75 45.8 44.6 46.8 47 44.95 43.7 44.9 48 ZnO 33.7529.5 37.5 34 34.8 31.8 29.1 31 32 PbO 3.0 8.0 1.3 4 5 7.85 7 7.4 3.2Li₂O — — — 1.4 — — — — — Na₂O 10.7 9.0 9.4 9.6 7.1 7.95 8.1 8.4 6.4 K₂O9.6 7.5 7.0 4 4.1 5 8 5.2 9.8 As₂O₃ 0.2 0.2 0.2 0.2 0.2 0.25 0.2 0.2 0.2MgO — — — — 1.8 — — — — CaO — — — — — 2.2 — — — B₂O₃ — — — — — — — — —Al₂O₃ — — — — — — — — — Y₂O₃ — — — — — — 3.9 — — GeO₂ — — — — — — — 2.9— F — — — — — — — — 0.4 ZnO + PbO 36.75 37.5 38.8 38 39.8 39.65 36.138.4 35.2 n_(d) 1.58 1.58 1.58 1.58 1.59 1.59 1.59 1.59 1.57 ν_(d) 48.048.0 50.1 48.9 48.4 47.1 48.0 47.3 50.5 τ_(1400 nm·25 mm) n.d. 0.9890.991 0.985 0.990 n.d. 0.984 n.d. n.d. Example 20 21 22 23 24 SiO₂ 4242.4 44.7 46.8 47.0 ZnO 34.9 38.6 39.9 38.6 38.2 PbO 12.5 8 — — — Na₂O7.2 7 7.9 7.4 8.2 K₂O 3.2 3.8 7.3 6.4 5.7 As₂O₃ 0.2 0.2 0.2 0.2 0.2 B₂O₃— — — 0.6 — Al₂O₃ — — — — 0.7 ZnO + PbO 47.4 46.6 39.9 38.6 38.2 n_(d)1.61 1.61 1.58 1.58 1.58 ν_(d) 44.1 45.8 50.4 50.6 50.5τ_(1400 nm·25 mm) 0.999 0.997 0.985 0.997 0.991

One feature of the invention resides broadly in the zinc-containingoptical glass materials with a refractive index of 1.52≦n_(d)≦1.66 andan Abbe number of 35≦ν_(d)≦54, characterized by the followingcomposition (in % by weight based on oxide)

SiO₂ 38–58 ZnO 0.3–42  PbO    0–<30 with ZnO + PbO 20–55 Li₂O   0–<3Na₂O  0–14 K₂O  0–12 with Li₂O + Na₂O + K₂O ≧2 F 0–3 MgO 0–6 CaO   0–<5SrO 0–6 BaO     0–<0.9 B₂O₃   0–<1 Al₂O₃     0–<1.5 ZrO₂   0–<2and, if appropriate, refining agents in the customary amounts.

Another feature of the invention resides broadly in the optical glassmaterials with a refractive index of 1.54≦n_(d)≦1.64 and an Abbe numberof 40≦ν_(d)≦52, characterized by the following composition (in % byweight based on oxide)

SiO₂ 39–54 ZnO 12–41 PbO  6–22 with ZnO + PbO 31–52 Li₂O   0–<3 Na₂O 0–13 K₂O  0–11 with Li₂O + Na₂O + K₂O ≧2 F 0–3 MgO 0–6 CaO   0–<5 SrO0–6 BaO     0–<0.9 B₂O₃   0–<1 Al₂O₃     0–<1.5 ZrO₂   0–<2and, if appropriate, refining agents in the customary amounts.

Yet another feature of the invention resides broadly in the opticalglass materials with a refractive index of 1.56≦n_(d)≦1.63 and an Abbenumber of 42≦ν_(d)≦52, characterized by the following composition (in %by weight based on oxide)

SiO₂ 40–55 ZnO 26–41 PbO  1–16 with ZnO + PbO 31–48 Li₂O   0–<3 Na₂O 0–12 K₂O  0–10 with Li₂O + Na₂O + K₂O ≧2 F 0–3 MgO 0–6 CaO   0–<5 SrO0–6 BaO     0–<0.9 B₂O₃   0–<1 Al₂O₃     0–<1.5 ZrO₂   0–<2and, if appropriate, refining agents in the customary amounts.

Still another feature of the invention resides broadly in the opticalglass materials with a refractive index of 1.60≦n_(d)≦1.63 and an Abbenumber of 43≦ν_(d)≦47, characterized by the following composition (in %by weight based on oxide)

SiO₂ 40–47 ZnO 32–41 PbO  5–14 with ZnO + PbO 40–48 Li₂O   0–<3 Na₂O 0–12 K₂O  0–10 with Li₂O + Na₂O + K₂O ≧2 F 0–3 MgO 0–6 CaO   0–<5 SrO0–6 BaO     0–<0.9 B₂O₃   0–<1 Al₂O₃     0–<1.5 ZrO₂   0–<2and, if appropriate, refining agents in the customary amounts.

A further feature of the invention resides broadly in the optical glassmaterials with a refractive index of 1.57≦n_(d)≦1.59 and an Abbe numberof 48≦ν_(d)≦52, characterized by the following composition (in % byweight based on oxide)

SiO₂ 41–50 ZnO 30–40 PbO 0–1 with ZnO + PbO 31–41 Li₂O   0–<3 Na₂O  0–11K₂O  0–10 with Li₂O + Na₂O + K₂O ≧2 F 0–3 MgO 0–6 CaO   0–<5 SrO 0–6 BaO    0–<0.9 B₂O₃   0–<1 Al₂O₃     0–<1.5 ZrO₂   0–<2and, if appropriate, refining agents in the customary amounts.

Another feature of the invention resides broadly in the optical glassmaterials characterized in that the glass materials contain up to 5% byweight Rb₂O, La₂O₃, Y₂O₃, and/or GeO₂.

Yet another feature of the invention resides broadly in the opticalglass materials characterized in that the glass materials contain up toat most 2.5% by weight Cs₂O.

Still another feature of the invention resides broadly in the opticalglass materials characterized in that the pure transmission of the glassmaterials, determined at 400 nm and 25 mm specimen thickness, is atleast 0.98.

A further feature of the invention resides broadly in the optical glassmaterials characterized in that the glass materials contain up to 8% byweight of coloring components.

Another feature of the invention resides broadly in the optical glassmaterials characterized in that the glass materials contain in total upto 1% by weight As₂O₃ and/or Sb₂O₃.

In accordance with one aspect, the present invention concerns azinc-containing optical glass with a refractive index (n_(d)) beingsubstantially in the range of from about 1.52 to about 1.66 and an Abbenumber (ν_(d)) being substantially in the range of from about 35 toabout 54, said zinc-containing optical glass substantially comprising,on an oxide basis, the composition of:

Percentage Material by weight SiO₂ 38–58 ZnO 0.3–42  PbO    0–<30 withZnO + PbO 20–55 Li₂O   0–<3 Na₂O  0–14 K₂O  0–12 with Li₂O + Na₂O + K₂O≧2 F 0–3 MgO 0–6 CaO   0–<5 SrO 0–6 BaO     0–<0.9 B₂O₃   0–<1 Al₂O₃    0–<1.5 ZrO₂    0–<2.

In accordance with another aspect, the invention concerns azinc-containing optical glass with a refractive index (n_(d)) beingsubstantially in the range of from about 1.57 to about 1.59 and an Abbenumber (ν_(d)) being substantially in the range of from about 48 toabout 52, said zinc-containing optical glass substantially comprising,on an oxide basis, the composition of:

Percentage Material by weight SiO₂ 41–50 ZnO 30–40 PbO 0–1 with ZnO +PbO 31–41 Li₂O   0–<3 Na₂O  0–11 K₂O  0–10 with Li₂O + Na₂O + K₂O ≧2 F0–3 MgO 0–6 CaO   0–<5 SrO 0–6 BaO     0–<0.9 B₂O₃   0–<1 Al₂O₃    0–<1.5 ZrO₂    0–<2.

In accordance with a further aspect of the invention there is provided amethod of forming zinc-containing optical glass which consists of, on anoxide basis:

Percentage Material by weight SiO₂ 38–58 ZnO 0.3–42  PbO    0–<30 withZnO + PbO 20–55 Li₂O   0–<3 Na₂O  0–14 K₂O  0–12 with Li₂O + Na₂O + K₂O≧2 F 0–3 MgO 0–6 CaO   0–<5 SrO 0–6 BaO     0–<0.9 B₂O₃   0–<1 Al₂O₃    0–<1.5 ZrO₂   0–<2said zinc-containing optical glass having a refractive index (n_(d))substantially in the range of from about 1.52 to about 1.66 and an Abbenumber (ν_(d)) substantially in the range of from about 35 to about 54,said method including the steps of:

(a) mixing and melting raw materials comprising said oxides to form abatch of glass;

(b) heating a batch of glass obtained in accordance with step (a) toproduce a melt of zinc-containing optical glass;

(c) refining said melt obtained in accordance with step (b) with a atleast one refining agent, said refining agent being added in an amountsufficient to refine said zinc-containing optical glass.

Zinc-containing optical glass in accordance with the present inventionmay, for example, have any value of refractive index (n_(d)) in therange of from about 1.52 to about 1.66, for example, 1.53 and 1.65.Thus, the value of refractive index (n_(d)) is not limited to the firstand final values of the range, but can comprise any value of refractiveindex (n_(d)) between them.

The zinc-containing optical glass in accordance with the presentinvention may, for example, have any Abbe number (ν_(d)) in the range offrom about 35 to about 54, for example, 36 and 53. Accordingly, the Abbenumber (ν_(d)) is not limited to the first and final values of therange, but can comprise any value between them.

Zinc-containing optical glass of the present invention may, for example,have a zinc content, in percent by weight based on oxide, in the rangeof from about 0.3 to about 42 percent by weight, for example, 0.4 and41.9. Thus, the amount of zinc content, in percent by weight based onoxide, is not limited to the first and final values of the indicatedrange, but can comprise any value between them.

The zinc-containing optical glass of the invention may, for example,have a ZnO plus PbO content in the range of from about 21 to about 55percent by weight based on oxide, for example, 21.5 and 54.5.Accordingly, the content of ZnO plus PbO, by weight based on oxide, isnot limited to the first and final values of the indicated range, butcan comprise any value between them.

The zinc-containing optical glass in accordance with our invention cancomprise a total content of CaO plus SrO in the range of from 0 to about5 percent by weight based on oxide, for example, 0.5 and 4.9. Thus, thecontent of CaO plus SrO, by weight based on oxide, is not to be limitedto the first and final values of the indicated range, but can compriseany value between them.

Other components of the composition of the zinc-containing optical glassof the present invention are likewise not limited to the first and finalvalues of the indicated range, but can comprise any value between them.

The features disclosed in the various publications, disclosed orincorporated by reference herein, may be used in the embodiments of thepresent invention, as well as, equivalents thereof.

All, or substantially all, of the components and methods of the variousembodiments may be used with at least one embodiment or all of theembodiments, if more than one embodiment is described herein.

All of the patents, patent applications and publications recited herein,and in the Declaration attached hereto, are hereby incorporated byreference as if set forth in their entirety herein.

The corresponding foreign application, namely, Federal Republic ofGermany Patent Application No. 199 58 522.9, filed on Dec. 4, 1999,having inventors Dr. Ina MITRA, Danuta GRABOWSKI, Dr. Uwe KOLBERG, andPaul KIβL, as well as their published equivalents, and other equivalentsor corresponding applications, if any, in corresponding cases in theFederal Republic of Germany and elsewhere, and the references cited inany of the documents cited herein, are hereby incorporated by referenceas if set forth in their entirety herein, are hereby incorporated byreference as if set forth in their entirety herein.

The details in the patents, patent applications and publications may beconsidered to be incorporable, at Applicants' option, into the claimsduring prosecution as further limitations in the claims to patentablydistinguish any amended claims from any applied prior art.

Although only a few exemplary embodiments of this invention have beendescribed in detail above, those skilled in the art will readilyappreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of this invention. Accordingly, all such modifications areintended to be included within the scope of this invention as defined inthe following claims. In the claims, means-plus-function clauses areintended to cover the structures described herein as performing therecited function and not only structural equivalents but also equivalentstructures.

Examples of optical glass containing zinc and the use thereof may befound in U.S. Pat. No. 5,754,290 issued on May 19, 1998 to Rajic, et al.and entitled “Monolithic spectrometer”; U.S. Pat. No. 5,524,133 issuedon Jun. 4, 1996 to Neale, et al. and entitled “Material identificationusing x-rays”; U.S. Pat. No. 5,356,840 issued on Oct. 18, 1994 to Nodaand entitled “Distributed index of refraction type optical element andmethod of making the same”; U.S. Pat. No. 4,981,331 issued on Jan. 1,1991 to Taylor and entitled “Low reflection optical reticle and methodof making same”; and U.S. Invention Registration No. H158 published onNov. 4, 1986 to Fraustro, et al. and entitled “Method of bonding anelectrically conductive material to an electrically conductive layerwhich overlies a curved non-metallic substrate”.

Examples optical glass including the manufacture, shaping and usethereof may be found in U.S. Pat. No. 6,127,297 issued on Oct. 3, 2000to Hashimoto and entitled “Optical glass having a low specific gravity”;U.S. Pat. No. 5,824,615 issued on Oct. 20, 1998 to Chang and entitled“Optical glass composition for precise press molding”; U.S. Pat. No.5,735,920 issued on Apr. 7, 1998 to Omori, et al. and entitled “Methodof manufacturing optical glass element”; U.S. Pat. No. 5,607,886 issuedon Mar. 4, 1997 to Onozawa and entitled “Optical glass for mold pressinghaving softening capability at low temperature”; U.S. Pat. No. 5,472,918issued on Dec. 5, 1995 to Onozawa and entitled “Optical glass”; U.S.Pat. No. 5,346,522 issued on Sep. 13, 1994 to Komiyama, et al. andentitled “Method and apparatus for molding optical glass elements or thelike”; U.S. Pat. No. 5,332,700 issued on Jul. 26, 1994 to Yamaguchi, etal. and entitled “High dispersion optical glass”; U.S. Pat. No.5,320,987 issued on Jun. 14, 1994 to Senoo, et al. and entitled “Opticalglass”; U.S. Pat. No. 5,217,516 issued on Jun. 8, 1993 to Ishiguro, etal. and entitled “Method of making optical glass article”; U.S. Pat. No.5,087,279 issued on Feb. 11, 1992 to Monji, et al. and entitled “Methodof producing optical glass element and production apparatus using thismethod”; U.S. Pat. No. 5,022,904 issued on Jun. 11, 1991 to Ishiguro etal. and entitled “Method of making optical glass article”; U.S. Pat. No.4,996,173 issued on Feb. 26, 1991 to Tachiwara and entitled “Opticalglass”; U.S. Pat. No. 4,771,020 issued on Sep. 13, 1988 to Omata et al.and entitled “Optical glass”; U.S. Pat. No. 4,732,875 issued on Mar. 22,1988 to Sagara and entitled “Optical glass”; U.S. Pat. No. 4,481,299issued on Nov. 6, 1984 to Tajima and entitled “Optical glass”; U.S. Pat.No. 4,472,030 issued on Sep. 18, 1984 to Tachibana et al. and entitled“Cesium-containing optical glass”; U.S. Pat. No. 4,439,530 issued onMar. 27, 1984 to Tajima and entitled “Optical glass”; U.S. Pat. No.4,426,216 issued on Jan. 17, 1984 to Sato, et al. and entitled “Processfor producing optical glass”; U.S. Pat. No. 4,144,076 issued on Mar. 13,1979 to Matsumaru and entitled “Optical glass”; U.S. Pat. No. 4,128,432issued on Dec. 5, 1978 to Komorita and entitled “Optical glass”; U.S.Pat. No. 4,119,471 issued on Oct. 10, 1978 to Komorita et al. andentitled “Optical glass”; U.S. Pat. No. 4,115,131 issued on Sep. 19,1978 to Ishibashi et al. and entitled “Optical glass”; U.S. Pat. No.3,958,999 issued on May 25, 1976 to Izumitani, et al. and entitled“Optical glass”; and U.S. Pat. No. 3,954,431 issued on May 4, 1976 toFleming, Jr. et al. and entitled “Optical glass and its production”.

Optical glass fiber examples may be found in U.S. Pat. No. 6,004,675issued on Dec. 21, 1999 to Akasaka et al. and entitled “Optical glassfiber”; U.S. Pat. No. 4,345,036 issued on Aug. 17, 1982 to Bamford etal. and entitled “Optical glass fibers and method of forming suchfibers”; U.S. Pat. No. 4,297,141 issued on Oct. 27, 1981 to Tokunaga etal. and entitled “Optical glass for optical paths”; U.S. Pat. No.4,159,863 issued on Jul. 3, 1979 to Stewart and entitled “Coupling ofoptical glass fibers”; and U.S. Pat. No. 4,145,200 issued on Mar. 20,1979 to Yamazaki et al. and entitled “Production of optical glassfibers”.

This invention as described hereinabove in the context of the preferredembodiments is not to be taken as limited to all of the provided detailsthereof, since modifications and variations thereof may be made withoutdeparting from the spirit and scope of the invention.

1. A zinc-containing optical glass with a refractive index (n_(d)) beingin the range of from about 1.52 to about 1.66 and an Abbe number (V_(d))being substantially in the range of from about 35 to about 54, saidzinc-containing optical glass comprising, on an oxide basis, thecomposition of: Percentage Material by weight SiO₂ 38–58 ZnO 0.3–42  PbO   0–<30 sum of ZnO + PbO >30–55   Li₂O   0–<3 Na₂O  0–14 K₂O  0–12 sumof ≧2 Li₂O + Na₂O + K₂O F 0–3 MgO 0–6 CaO   0–<5 SrO 0–6 BaO     0–<0.9B₂O₃   0–<1 Al₂O₃     0–<1.5 ZrO₂   0–<2 Cs₂O 0 to about 2.5; ≧0% byweight of at least one refining agent.


2. The zinc-containing optical glass according to claim 1, wherein saidglass further comprises 0 to about 5% by weight of one member of thegroup and combinations thereof: Rb₂O, La₂O₃, Y₂O₃, and GeO₂.
 3. Thezinc-containing optical glass according to claim 2, wherein the lighttransmission of the glass, determined at a wavelength of 400 nm and a 25mm specimen thickness, is at least about 0.98.
 4. The zinc-containingoptical glass according to claim 3, wherein said glass further comprises≧0% by weight of a coloring component.
 5. The zinc-containing opticalglass according to claim 4, wherein said coloring component is a memberof the group and combinations thereof: CuO, Cr₂O₃, CoO, Fe₂O₃, MnO, NiO,and V₂O₅.
 6. The zinc-containing optical glass according to claim 5,wherein said glass comprises up to about 1% by weight of said at leastone refining agent.
 7. The zinc-containing optical glass according toclaim 6, wherein said glass comprises up to about 0.5% by weight of saidat least one refining agent.
 8. The zinc-containing optical glassaccording to claim 7, wherein said at least one refining agent is atleast one member of the group and combinations thereof: As₂O₃, andSb₂O₃.
 9. The zinc-containing optical glass according to claim 8,wherein CaO plus SrO is in the range of from 0 to 5% by weight.
 10. Anoptical filter comprising zinc-containing optical glass, wherein thezinc-containing optical glass is according to claim
 1. 11. Azinc-containing optical glass with a refractive index (n_(d)) being inthe range of from about 1.52 to about 1.66 and an Abbe number (V_(d))being substantially in the range of from about 35 to about 54, saidzinc-containing optical glass consisting of, on an oxide basis, thecomposition of: Percentage Material by weight SiO₂ 38–58 ZnO 0.3–42  PbO >0–<30 sum of ZnO + PbO 20–55 Li₂O   0–<3 Na₂O  0–14 K₂O  0–12 sum ofLi₂O + Na₂O + K₂O ≧2 F 0–3 MgO 0–6 CaO   0–<5 SrO 0–6 BaO     0–<0.9B₂O₃   0–<1 Al₂O₃     0–<1.5 ZrO₂   0–<2 Cs₂O 0 to about 2.5 ≧0% byweight of at least one refining agent.


12. The zinc-containing optical glass according to claim 11, wherein thesum of ZnO plus PbO is in the range of >21 to 55% by weight.
 13. Thezinc-containing optical glass according to claim 12, wherein: CaO plusSrO is in the range of from 0 to 5% by weight; the light transmission ofthe glass, determined at a wavelength of 400 nm and a 25 mm specimenthickness, is at least about 0.98; up to a total of about 1% by weightof said at least one refining agent is present; and said at least onerefining agent is at least one member of the group and combinationsthereof: As₂O₃ and Sb₂O₃.
 14. The zinc-containing optical glassaccording to claim 13, wherein up to a total of about 0.5% by weight ofsaid at least one refining agent is present.
 15. A zinc-containingoptical glass with a refractive index (n_(d)) being in the range of fromabout 1.52 to about 1.66 and an Abbe number (V_(d)) being substantiallyin the range of from about 35 to about 54, said zinc-containing opticalglass consisting of, on an oxide basis, the composition of: PercentageMaterial by weight SiO₂ 38–58 ZnO 0.3–42  PbO  >0–<30 sum of ZnO + PbO20–55 Li₂O   0–<3 Na₂O  0–14 K₂O  0–12 sum of Li₂O + Na₂O + K₂O ≧2 F 0–3MgO 0–6 CaO   0–<5 SrO 0–6 BaO     0–<0.9 B₂O₃   0–<1 Al₂O₃     0–<1.5ZrO₂   0–<2 Cs₂O 0 to about 2.5;

0 to about 5% by weight of one member of the group and combinationsthereof: Rb₂O, La₂O₃, Y₂O₃, and GeO₂; ≧0% by weight of one member of thegroup and combinations thereof: CuO, Cr₂O₃, CoO, Fe₂O₃, MnO, NiO, andV₂O₅; and ≧0% by weight of at least one refining agent.
 16. Thezinc-containing optical glass according to claim 15, wherein the lighttransmission of the glass, determined at a wavelength of 400 nm and a 25mm specimen thickness, is at least about 0.98.
 17. The zinc-containingoptical glass according to claim 16, wherein said at least one refiningagent is in the range of ≧0% up to about 1% by weight.
 18. Thezinc-containing optical glass according to claim 17, wherein said atleast one refining agent is in the range of ≧0% up to about 0.5% byweight.
 19. The zinc-containing optical glass according to claim 18,wherein said at least one refining agent is at least one member of thegroup and combinations thereof: As₂O₃ and Sb₂O₃.
 20. The zinc-containingoptical glass according to claim 19, wherein CaO plus SrO is in therange of from 0 to 5% by weight.